Conventionally, conveying apparatuses are known that sort conveyed items such as postal items or the like according to a predetermined classification. This type of conveying apparatus separates and takes out the conveyed items one by one from a take-out portion, conveys them spaced apart from one another with a conveyor belt or the like, and collects them in a collecting portion. Here, there are individual differences among the conveyed items, so that the conveying speed of each item may change depending on these individual differences. When the conveying speed changes in this way, the spacing between conveyed items may become too wide or too narrow. Thus, there is the possibility that during the operation of sorting or collecting the conveyed items, problems occur and a stable collection cannot be achieved.
For this reason, a gap correction device for adjusting the conveying speed of the conveyed items is provided midway in the conveyance of the conveyed items. By adjusting the conveying speed of the conveyed items with this gap correction device, the gap (referred to as “preceding gap” in the following”) between a conveyed item whose gaps are to be corrected (also referred to as “conveyed item subject to correction” in the following) and the conveyed item that is conveyed immediately in front of that conveyed item subject to correction (referred to as “preceding conveyed item” in the following) can be corrected. Moreover, the gap (referred to as “following gap” in the following”) between the conveyed item subject to correction and the conveyed item that is conveyed immediately behind that conveyed item subject to correction (referred to as “following conveyed item” in the following) can be corrected. Here, the adjustment of the conveying speed with the gap correction device is decided based on the difference between the preceding gap and the following gap. Thus, the preceding gap and the following gap of the conveyed item subject to correction that has passed the gap correction device can be kept within a predetermined range.
However, in practice, also the conveying speed of the conveyed items subject to correction varies when they pass the gap correction device, so that it may be difficult to keep the preceding gap and the following gap of the conveyed item subject to correction that has passed the gap correction device within the predetermined range. That is to say, when the thickness of the conveyed items is large, for example, then the adjustment speed is lower than in the case of thin conveyed items. Therefore, for conveyed items of different thicknesses, it may be difficult to correct the preceding gaps and the following gaps of all conveyed items with high precision.